Pavement Stabilization Techniques to Restore Flood-Affected Roads in Queensland

In 2011, a severe flooding event affected the entire state of Queensland in Australia. This resulted in pavement damage to many thousands of kilometers of state and regional council controlled roads. The pavements of the most affected roads consisted of granular layers with multiple sprayed seals constructed over weak, highly reactive natural subgrades. The natural subgrades often exhibited high swelling potential that, coupled with poor road geometry and drainage, often led to large seasonal fluctuation in moisture content of the subgrade. Techniques, such as foamed bitumen stabilization and cement modification of the existing pavement layers, have often been adopted. A range of stabilizing agents, such as foamed bitumen and an array of cementitious stabilizing agents, has been utilized under different circumstances to achieve the best project outcome. Field and laboratory investigations were undertaken to assess the post-flood condition of the road network, as well as to determine the suitability and reactivity of each stabilizing agent to the wide range of base aggregate sources found throughout the network. This paper presents the findings from field and laboratory investigations undertaken on the flood-affected pavements of four regional roads near Ipswich in South East Queensland. These investigations were undertaken to characterize existing pavement materials and to evaluate the performance of existing granular materials stabilized with foamed bitumen or modified with cementitious stabilizing agents. To evaluate the mixes of granular materials and stabilizing agents, the results from tests conducted on samples of existing imported granular materials stabilized or modified with foamed bitumen or cementitious binders were compared against a set of Australian developed mix design criteria. Furthermore, this paper summarizes the advantages and disadvantages of both the cementitious modification and foamed bitumen stabilization techniques and summarises the manners in which these layers were modeled.